1. Field of the Invention
The present invention generally relates to hoist apparatus for use in lifting and lowering personnel and materials in confined spaces and, more particularly, is concerned with a boom lift apparatus mountable to a plurality of different support structures.
2. Description of the Prior Art
A variety of diverse hoists are found in the prior art for lifting, lowering and moving loads from one location to another. Some of these hoists are portable in nature in that they are mountable, for instance, on a bumper, load bed, box or other part of a vehicle, such as a pickup truck, in a deployed condition during periods of use and then can be converted to a collapsed position for storage during periods of nonuse.
Representative examples of these hoists in the prior art are the ones disclosed in U.S. patents to Adams (U.S. Pat. No. 2,661,854), Wardlaw (U.S. Pat. No. 3,899,089), Harlan (U.S. Pat. No. 4,671,731) and Van Staveren (U.S. Pat. No. 5,054,078). Another example of a hoist is an apparatus identified as a DBI/SALA.TM. davit arm system marketed by D B Industries, Inc. of Red Wing, Minn. Both the DBI davit arm and the hoist of the Van Staveren patent have similar overall constructions. Each employs a lower vertical mast and an upper boom arm pivotally mounted in an inclined relationship to the lower vertical mast for undergoing movement in a vertical plane relative to the vertical mast. The upper boom arm of Van Staveren is telescopically extendable and Can be actuated (raised or lowered) relative to the lower vertical mast by action of a hydraulic cylinder pivotally attached between the lower vertical mast and upper boom arm. The upper boom arm of the BDI/SALA.TM. davit arm system supports a winch and cable for use in lifting and lowering loads.
While the overall construction of the DBI/SALA.TM. davit arm and the hoist of the Van Staveren patent appears to be a step in the right direction, both of these hoists appear to be restricted to a particular type of location where they can be employed to assist in lifting and moving loads. Consequently, a need still exists for a boom lift assembly which will overcome the restrictions of the prior art, particularly of the DBI/SALA.TM. davit arm and the Van Staveren hoist.